x三次方+2x²-2x-1=0

x三次方+2x²-2x-1=0
x三次方+2x²-2x-1=0

x三次方+2x²-2x-1=0

x^3-1+2x^2-2x=0
(x-1)(x^2+x+1)+2x(x-1)=0
(x-1)(x^2+3x+1)=0
x=1或x=(-3±√5)/2

f(x) =x^3+2x^2-2x-1
f(1)=0
x^3+2x^2-2x-1=(x-1)(x^2+ax+1)
coef. of x
-a-2 = -2
a= 0
x^3+2x^2-2x-1=(x-1)(x^2+1)=0
x=1

X^3-1+2X(X-1)=0
(X-1)((X+3/2)^2-5/4)=0
X=1或X=(3加减根号5)/2